The bottoms of vessels, structures in seawater, and fishing nets are immersed in seawater for prolonged periods during use and thus there arises a problem that adhesion and growth of various aquatic organisms, for example, marine animals such as oysters, hard-shelled mussels and barnacles, plants such as layer, or bacteria, on the surface, impair the appearance and the function thereof. Particularly, adhesion and growth of these aquatic organisms on vessel bottoms increase the surface roughness, thereby reducing the vessel speed and the fuel efficiency. A great deal of labor is required to remove these aquatic organisms from the vessel bottoms.
To prevent damage due to adhesion of aquatic organisms, an antifouling coating having excellent antifouling properties, for example, a coating containing a copolymer of tributyltin methacrylate (hereinafter abbreviated to TBTMA) and cuprous oxide, has hitherto been coated on the vessel bottoms. The coating film obtained from the antifouling coating can always maintain an active surface as a so-called “hydrolyzable self-polishing type coating film” which exerts an antifouling effect by releasing an organotin compound such as hexabutyldistannoxane or tributyltin halide as a result of hydrolysis of the copolymer in seawater.
However, since the organotin compound produced by hydrolysis of the copolymer of TBTMA is highly toxic, there is fear of adverse effects on the ecosystem due to ocean pollution.
Japanese Examined Patent Application, Second Publication No. Sho 63-61989 discloses a technology of using an antifouling coating containing a tin-free polymer as a vehicle component, wherein cuprous oxide as an antifouling agent is released as a result of dissolution of a matrix resin, thereby imparting antifouling properties. The vehicle component (a matrix resin) used in this technology is an alkoxyalkyl acrylate homopolymer or a copolymer of an alkoxyalkyl acrylate and a monomer containing no carboxyl or hydroxyl group.
However, the antifouling coating described in Japanese Examined Patent Application, Second Publication No. Sho 63-61989 is actually insufficient in solubility and in hydrolyzability of the matrix resin in seawater because the coating is designed considering the film strength of major importance. Consequently, practical antifouling properties could not be obtained.